During the forthcoming year we plan to further characterize the membrane protein of the adrenal medulla chromaffin vesicles, to better define the ATPase activity of the membranes with the purpose of better elucidating its role in vesicle function and to initiate studies on the purification of the plasma membranes of adrenal medullary cells. Secondarily we plan to continue studes of chick adrenal glands in organ culture in attempts to define conditions which will enable them to induce tyrosine hydroxylase and recover their catecholamine stores after carbamylcholine-evoked secretion.